Dual wavelength and switchable laser operation of Pr3+:LiYF4 crystals at 523 nm and 640 nm

Solid state lasers in the visible spectral region have many possible applications like projection technology and spectroscopy [1,2]. In these fields the generation of green light is still a challenge. Recent projection devices generate green laser light by frequency doubling of near-infrared solid state laser radiation. A compact, simple, and efficient laser based projection device is not yet developed. The trivalent Pr3+ ion in the host material LiYF4 (YLF) has several transitions at wavelengths in the visible spectral range, for example at 523 nm (green) or at 640 nm (red). Pr:YLF can be efficiently pumped by GaInN laser diodes at 444 nm (blue) [3].